Is there going to be an option to abort the complete transaction without 
knowing how deep you are?  Perhaps something like "ABORT ALL".
The reason I suggest this, is that I can foresee an application or user 
leaving nested transactions open inadvertently, or not knowing how 
deeply nested they are when they are called.  It's just a thought, and I 
didn't recall any mention of something like it on the list.
Thomas